Comparative study on fracture characteristics of coal and rock samples based on acoustic emission technology

Abstract

Monitoring on the damage evolution process of the coal and rock mass in coal resource mining play a vital role in safe production and avoiding economic losses. This study aims at further improving effectiveness and accuracy of acoustic monitoring method in the process of coal resource mining. For this purpose, a rock mechanics testing system and an acoustic emission (AE) test system are employed to conduct AE event location experiments on the coal and rock samples under uniaxial loading. According to the basic theory of b-value and single-link cluster (SLC) method, changing trend of related parameters with stress is studied, including b-value, spatial correlation length ξ and information entropy H. Then, the reason for variation of these three parameters is revealed. The analysis results show that b-value has not obvious change at the initial stage of loading, but spatial correlation length ξ presents upward trend during this period. Compared with b-value and spatial correlation length ξ, information entropy H is not sensitive to damage state of the coal and rock sample during the most time of loading process. However, it is worth noting that that these three parameters show significant change trend before the buckling failure of the coal and rock samples. Based on three-dimensional crack growth theory and criterion of microcrack density, the research results show that the change of the parameters are the macro characterization of transformation process from small-scale microfracture to large-scale microfracture and from local damage to overall damage for the coal and rock samples subjected to uniaxial loading. This research provides a new method to evaluate the damage state of the coal and rock mass under high stress using AE source location technology, and it has important guiding significance and reference value for ensuring the safety of life and property in the process of coal resource mining.